The present invention relates to apparatus for holding and conveying articles, and more particularly to turrets for rotatably conveying large containers.
One well known type of apparatus for holding containers and other articles during processing is the so-called turret. The turret engages one or more articles and rotatably conveys these articles during decoration, filling, and other processing steps.
One typical class of apparatus incorporating such turrets is the decorating apparatus shown generally in FIG. 1. The decorator 100 transfers labels from a carrier web 150 to articles held in a rotating turret 10. The label transport includes unwind roll 110, metering roll 120, a shuttle 130 with shuttle rolls 133 and 137, rewind roll 140, and various dancer and idler rolls. Labels are pressed from carrier web 150 onto articles by a transfer roll 33. Drive mechanisms not shown regulate the web transport; this is coordinated with the indexing of the turret 10 by means of a turret shuttle arm 68.
Turrets are commonly characterized by intermittent motion, whereby the turret is indexed through a given angle to deliver each succeeding article to or through a processing station. In the case of turrets for holding articles of substantial size, this stop and go motion has engendered a number of mechanical problems. Prior art intermittent motion turret designs have typically incorporated a stationary brake to prevent the rotating elements of the turret from overtravelling; a considerable braking force is required in the case of turrets for conveying large articles.
FIG. 2 shows in section prior art mounting apparatus for a rotating turret such as the turret 10 of FIG. 1. The turret includes a central shaft 11 encased in a spindle 15. Attached to the spindle 15 are various rotor devices including an article cup 30 and article-engaging spiders 13, which periodically rotate counterclockwise along with the spindle through a given angle (such as 90.degree. for a four-station turret). Spindle 15 is fitted to a ratchet 45, while shaft 11 is fitted to a pawl plate 36. Pawl plate 36 is oscillated through a given angle by means of a rack and pinion assembly consisting of pinion gear 61, rack 62, and tube 63 driven by a shuttle arm 68 (FIG. 1).
During the forward, counterclockwise segment of this oscillation, the pawl plate 36 drives the ratchet 45 by engaging it with pawl 35. During the remainder of each cycle, a stationary brake 40 prevents overtravelling of ratchet 45. The driving mechanisms of turret 10 must overcome brake 40 during the forward cycle, which requires a considerable accelerating force for a turret of substantial size. This results in significant machine stresses and a tendency toward vibration during the forward cycle. In the decorator of FIG. 1, such machine vibration causes a periodic distortion of the imprinted image.
Accordingly, it is a primary object of the invention to provide an improved turret design which is especially suitable for conveyance of articles in a turret of relatively large diameter. A related object is the minimization of mechanical problems associated with such turrets. A further related object is the provision of a machine design which minimizes rotational drive forces required during the forward cycle of turret oscillation.
Another object of the invention is the achievement of a turret to hold large articles during decoration. A related object is the enhancement of image quality for inscribed indicia. A further related object is the avoidance of periodic image distortion associated with turret vibration.